Relationship between skin color and blood pressure in Egyptian adults - Results from the National Hypertension Project

In many, but not all societies, dark skin color is associated with high blo od pressure. Whether the association between skin color and blood pressure is independent of known determinants of blood pressure remains controversia l. We examined the association between skin color and blood pressure in 835 Egyptian adults (370 men and 465 women) participating in the National Hype rtension Project, a national survey of hypertension prevalence and blood pr essure-related complications conducted in Egypt during 1991-1993. Skin colo r was assessed by measuring the concentration of cutaneous melanin in an un exposed area with the use of reflectance spectrophotometry. Higher concentr ations of melanin were associated with lower body mass index, less educatio n, manual labor (among men), and a lower urinary sodium-to-potassium ratio (among women). In multivariate regression analyses adjusted for age, body m ass index, and education, there was a significant nonlinear association bet ween blood pressure and skin color among women; in the lower to intermediat e range of skin pigmentation, both systolic and diastolic blood pressures w ere higher in women with greater concentrations of cutaneous melanin. In me n, blood pressure was not associated with skin color. When we used a subjec tive assessment of skin color, there was no significant difference in blood pressure between black-skinned Egyptians (predominantly of Nubian descent) and fair-skinned Egyptians for either gender. While the significant relati onship in women appeared to be independent of known risk factors for hypert ension, residual confounding may explain the association.